MIDL VARIANT-type to proper C# type

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Bjoern - 24 Sep 2007 22:51 GMT

Hi

I have a COM object which fires an event where I have to pass an array
of SHORTs as a parameter to the listening object. The array of SHORTs
is encapsulated in a the CComSafeArray-class and passed as a VARIANT*
in MIDL (since MIDL doesn't support SAFEARRAYs in events).

In C# (.NET 1.0) the MIDL VARIANT* data-type is registered as "ref
object" in the event-handler (delegate). How do I convert this "ref
object" to a short array?

-- Bjoern

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Mattias Sjögren - 25 Sep 2007 04:53 GMT

>How do I convert this "ref
>object" to a short array?

You probably only need a cast.

void YourEventHandler(ref object o)
{
short[] arr = (short[])o;
// Do stuff...
}

If that doesn't work please tell us what o.GetType().FullName returns.

Mattias

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Mattias Sjögren [C# MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
Please reply only to the newsgroup.

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Bjoern - 26 Sep 2007 21:58 GMT

Hi

When I get the full path of the VARIANT* type it says
"System.Boolean".

Here's how my IDL event is declared:

HRESULT OnUserAudioData([in] LONG nUserID, [in] LONG nSampleRate, [in]
VARIANT* pRawAudio, [in] LONG nSamples);

Here's how I pass my data to the event:

//-- begin
Audio* aud = reinterpret_cast<Audio*> (lParam);
CComSafeArray<SHORT, VT_I2> safeArray;
if(aud->samples)
safeArray.Add(aud->samples, aud->rawAudio, TRUE);
CComVariant vtVar(safeArray);
m_pListener->Fire_OnUserAudioData(aud->userid, aud->samplerate,
&vtVar, aud->samples);
//-- end

Any idea why C# thinks it's a boolean?

-- Bjoern

On Sep 25, 5:53 am, Mattias Sj?gren <mattias.dont.want.s...@mvps.org>
wrote:

> >How do I convert this "ref
> >object" to a short array?
[quoted text clipped - 15 lines]
> Mattias Sj?gren [C# MVP] mattias @ mvps.orghttp://www.msjogren.net/dotnet/|http://www.dotnetinterop.com
> Please reply only to the newsgroup.

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MIDL VARIANT-type to proper C# type

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